A recent publication in the Journal of Chemical Education caught my eye.¹ The article describes how lithium “coin” or “button” batteries can be used in the chemistry laboratory to teach students about stoichiometry. The authors describe how to use lithium metal extracted from these batteries to study the stoichiometry of the chemical reaction between lithium and water:

2 Li(s) + 2 H₂O (l) → 2 Li⁺(aq) + 2 OH^-(aq) + H₂(g)            Eq. 1

After reading this article, I was inspired to try some of my own experiments with coin batteries.² Specifically, I wanted to see if I could use lithium extracted from these batteries to generate the beautiful, pink flame observed in a lithium flame test. You can see the results of my explorations, along with a short description of lithium chemistry below (Video 1).

Video 1: Lithium Battery Flame, Tommy Technetium YouTube Channel, Sept. 26, 2021

Do you think I was I successful in using the lithium contained in these batteries to generate a pink flame? Let me know your thoughts in the comments. I should mention that the pink flame is quite easy to see even under room lights - especially when igniting bubbles resulting from dropping the lithium pieces into a Petri dish. The effect is just difficult to capture on film.

Chemistry of lithium coin batteries

I thought I’d share with you some of my thoughts about the chemistry involved in coin batteries. The Energizer company reports that lithium coin cells contain a lithium anode and MnO₂ cathode.^3-5 Thus, the overall reaction in a lithium coin battery can be described as:⁶

Li(s) + MnO₂(s) → MnOOLi(s)               E_cell = +3.0 V                          Eq. 2

Where the cell potential above is estimated from the fact that most coin batteries are listed at 3.0 V. The pertinent half reactions used to obtain the reaction described in Eq. 2 would be:

anode: Li⁺ + e^- → Li(s)                                               E⁰ = -3.04 V                Eq. 3

cathode: MnO₂(s) + Li⁺ + e^- → MnOOLi(s)              E⁰ = -0.04 V                Eq. 4

Note that the reduction potential for the reduction of lithium ion (Eq. 3) is well known.⁷ While I could not find a reference for the reduction potential of the process outlined in Eq. 4, it can be estimated by using Eq. 5:

E⁰_cell = E⁰_red – E⁰_ox                  Eq. 5

Where E⁰_cell is the overall cell potential for the battery, E⁰_red  is the reduction potential for the cathode half reaction and E⁰_ox is the reduction potential for the anode half reaction. Assuming the button batteries are constructed under standard conditions, inserting E⁰_cell = +3.0V and E⁰_ox = -3.04 V into Eq. 5, we find an estimate of -0.04 V for E⁰_ox.

Conclusion

Thus, in addition to the stoichiometric experiments described by the authors of the original article,¹ lithium coin batteries can be used as an interesting source for a lithium flame test as well as a springboard to discuss some concepts in electrochemistry. These experiments were quite well-received when I conducted them for some of my students. If you decide to try out these experiments in your classroom, be sure to use proper protection. Manufacturers of batteries often claim disassembling batteries can cause them to leak, explode, or cause fire. However, the authors of the article in the Journal of Chemical Education report they have opened hundreds of batteries with no observed risk,¹ and I have opened tens of batteries with no problems. Even so, I made sure to use gloves, goggles, and a labcoat when I attempted to open these batteries.

As always, let me know what you find if you try some of these experiments on your own. I'd also love to hear what other type of chemical topics you think might connect to the experiments described here.

Happy Experimenting!

References

1. V. A. Martínez and J. G. Ibanez, All Roads Lead to Rome: Triple Stoichiometry with a Lithium Battery, 2020, 97, 4103−4107.
2. Specifically, I used CR1616, CR2025, and CR2032 in my experiments.
3. Energizer Product Datasheet for CR2025 Lithium batteries, https://data.energizer.com/pdfs/cr2025.pdf
4. Energizer Product Datasheet for CR2032 Lithium batteries, https://data.energizer.com/pdfs/cr2032.pdf
5. Energizer Product Datasheet for CR1616 Lithium batteries, https://data.energizer.com/pdfs/cr1616.pdf
6. Maxwell CR (Coin Type Lithium Manganese Dioxide Battery) Datasheet, https://biz.maxell.com/en/primary_batteries/cr_coin.html
7. Harris, Daniel C. Quantitative Chemical Analysis (8th ed.). W. H. Freeman and Company. pp. AP20-AP29.